PC-Engine PC-Doctor 4M

**ConsoleFun** · 04-02-2007

Anyone know anything about this unit?

Top:

Under:

Back:

PCB:

2Mbit onboard + 2Mbit on memory board

CF

**Baseley09** · 04-02-2007

Looks to be usefull for the white pc engine, to add s-video & presumably stereo sound out over the headphone jack.

**ccovell** · 04-02-2007

It almost looks like a game copier/backup unit as well...
Have you tested it with a PC-Engine?

I'd also recommend covering up that EPROM window with some black tape if you plan to take any more photographs :-)

**ConsoleFun** · 04-02-2007

Originally Posted by ccovell

Have you tested it with a PC-Engine?

I only have a Duo-R. Looking for a Core Grafix now :)

Originally Posted by ccovell

I'd also recommend covering up that EPROM window with some black tape if you plan to take any more photographs :-)

I dumped the EPROM :)
Didn't see any strings... Can you recommend a disassembler?

CF

**Barc0de** · 04-02-2007

it says CD-RAM system, it says Doctor, and it has 4M written on it. Sounds like a coding tool. Maybe u can use the I/O to transfer images into its RAM and execute? Like a cheap devkit?

**Calpis** · 04-02-2007

Definitely a copier, definitely unusable without the parallel cable w/o reversing the circuit; else I would have bought it first! :P

Since the unit has DRAM, the PLD must contain registered logic which means reverse engineering isn't a reasonable option.

MAME has a free Hu6280 disassembler if you want to poke. Look through a tile editor for font patterns instead of ASCII strings, that'll be more fruitful.

Edit: also it doesn't add S-video (of course, there is no RGB encoder!), maybe it's compatible with MD2 cables, probably not though since it's probably older than MD2.

**Barc0de** · 04-02-2007

people should stop reffering to EVERY DINN-looking connector as S-video :P

**ConsoleFun** · 04-02-2007

Originally Posted by Barc0de

Maybe u can use the I/O to transfer images into its RAM and execute?

That would be pretty cool :)

Originally Posted by Calpis

MAME has a free Hu6280 disassembler if you want to poke. Look through a tile editor for font patterns instead of ASCII strings, that'll be more fruitful.

Thanks for your expert advice Calpis! I can confirm that a bitmap font occupies a large part of the ROM. Going to check out the MAME disassembler, but I was hoping there was a 6280-compatible CPU that IDA supports (65C02?)...

CF

**mdmx** · 04-02-2007

if it's a backup unit, I don't understand why it's mounted at the extension port. MGD1 and MGD2 use the Hu-Card slot.

Maybe it's a IFU clone?

**Calpis** · 04-02-2007

The expansion port contains everything from the Hucard slot and more, it also makes it look less suspicious.

65C02 wouldn't be close enough to the Hu6280, there are a lot of instructions that are new and perhaps replace old opcodes (which would make the output incoherent.) IDA also isn't that great of a disassembler for non intel code IMO, better to just disassemble manually with freeware tools.

**ConsoleFun** · 04-02-2007

Originally Posted by Calpis

65C02 wouldn't be close enough to the Hu6280, there are a lot of instructions that are new and perhaps replace old opcodes (which would make the output incoherent.)

It didn't look too good, so I think you're right, hehehe :))

Originally Posted by Calpis

IDA also isn't that great of a disassembler for non intel code IMO, better to just disassemble manually with freeware tools.

I think it rocks for Sega 68k. Doing pretty good on that Alma CDX thing... ;)

CF

**ASSEMbler** · 04-02-2007

The official dev kit does all functions via the exp port.

This has extemely important reverse engineering

possibilities for a diy homebrew dev kit.

**Calpis** · 04-02-2007

There is nothing to reverse engineer other than the unit itself which requires a lot of programmable logic which most people can't program anyway. Anyone wanting a "devkit" would be better off making a simpler homebrew one (see below) Because the unit has a BIOS, the interface is implemented in software with memory mapped registers for I/O to the parallel port.

PCE is one of the simplest consoles to make a "devkit" for since the cards are single 8bit ROMs and require no decoding logic. To make an in system programmable "EPROM-emulator" for PCE, you'd need a whopping $10 of off the shelf parts.

Rundown:
-SRAM (most expensive)
-address line counters
-tristates to isolate system/counter
-latches to control programming/isolation
(-if you want to get fancy, a MUX to "fix" address lines or this can be simulated in software.)
(-battery circuit (resistors, transistors, diodes, battery) could make it nonvolatile and hot swappable)

**ccovell** · 04-03-2007

PCEDis is an Okay PCE disassembler. I can't find the link to it, but I believe it was written by Dave Shadoff. (Or if you send the ROM dump to me, I can take a look at it...)